Method for fabricating semiconductor components using mold cavities having runners configured to minimize venting

ABSTRACT

A system for fabricating semiconductor components includes mating mold cavity plates having mold cavities configured to mold body segments of the semiconductor components on either side of a leadframe. The mold cavity plates also include runners configured to direct molding compound between the mold cavities and into the corners of the mold cavities. The runners prevent trapped air from accumulating in the corners of the mold cavities, and eliminate the need for air vents in the corners. The mold cavity plates also include dummy mold cavities configured to form dummy segments on the leadframe, and air vents in flow communication with the dummy segments. The dummy mold cavities are configured to collect trapped air, and to direct the trapped air through the air vents to atmosphere. Each dummy mold cavity has only a single associated air vent, such that cleaning is facilitated, and flash particles from the air vents are reduced. A method for fabricating semiconductor components includes a molding step performed using the system. A semiconductor component fabricated using the system includes the leadframe, a die, upper and lower body segments encapsulating the die, and dummy segments on the leadframe.

CROSS REFERENCE TO RELATED APPLICAIONS

This application is a division of Ser. No. 09/944,323, filed Aug. 30,2001, U.S. Pat. No. 6,969,918.

This application is related to Ser. No. 10/949,904, filed Sep. 24, 2004.

FIELD OF THE INVENTION

This invention relates generally to semiconductor packaging. Moreparticularly, this invention relates to a system and to a method forfabricating semiconductor packages using mold cavities having runnersconfigured to minimize venting.

BACKGROUND OF THE INVENTION

Semiconductor packages typically include a semiconductor dieencapsulated in a molded plastic body. The molded plastic bodyrigidifies and protects the die from the environment. Semiconductorpackages also include a substrate, such as a leadframe, or a circuitboard material, on which the die is mounted. The substrate includesconductors such as lead fingers for a leadframe, or conductive tracesfor a circuit board substrate which provide internal signal, power andground paths through the package body to the die. The package alsoincludes terminal contacts, such a metal leads, or solder balls, formaking electrical connections from the outside to the package.

The molded plastic body can be formed using a transfer molding process.During this process a mold cavity is placed on the substrate and overthe die, and a molding compound, such as an epoxy resin, is injectedinto the mold cavity. The molding compound can be injected on eitherside of the substrate to encapsulate the die and associated wire bonds.

A prior art transfer molding process is illustrated in FIG. 1. In thisexample the substrate comprises a metal leadframe 10. FIG. 1 illustratesonly a portion of the leadframe 10, which includes multiplesemiconductor dice 12 mounted in pairs across the width of the leadframe10. The leadframe 10 is an elongated member configured to fabricatemultiple semiconductor packages 14. Each package 14 includes a moldedplastic body 28 which encapsulates a die 12, and opposing surfaces on aportion of the leadframe 10.

The leadframe 10 includes openings 16A, 16B, 16C along longitudinaledges thereof, which facilitate handling by automated equipment such asconveyor tracks, magazines and loaders. The openings 16A, 16B, 16C alsofunction to align the leadframe 10 on various process systems such asdie attachers, wire bonders, molding systems, and singulation systems.The leadframe 10 also includes transverse thermal expansion slots 18 andleadfingers 20 that are wire bonded to bond pads (not shown) on the dice12. The leadfingers 20 are connected by bus bars 22, and willsubsequently be trimmed and formed into the terminal leads for thepackages 14. Further, the leadframe 10 includes a molding slot 24 whichfacilitates the flow of a molding compound 26 during molding of theplastic bodies 28.

As illustrated by the flow arrows 30, during the molding process themolding compound 26 is injected across the width of the leadframe 10from left to right in FIG. 1. A system for performing the moldingprocess includes mold cavities (not shown) clamped to the opposingsurfaces of the leadframe 10. During the molding process, trapped airbubbles 36 in the molding compound 26 can be released to a dummy moldcavity (not shown) which forms dummy segments 38 on the opposingsurfaces of the leadframe 10. However, some of the air is trapped at thecorners of the mold cavities, proximate to the corners 32 of the moldedplastic bodies 28. The trapped air requires that the molding systemincludes air vents 34 (indicated by dotted lines) in flow communicationwith the mold cavities proximate to the corners 32 of the molded plasticbodies 30.

One problem with the prior art molding system is that the air vents 34will typically fill with molding compound 26 during normal production.At given intervals the air vents 34 must be cleaned, which requires thatany molding compound 26, and also any cleaning compound in the air vents34, be scrapped out and removed. In view of the large number of airvents 34 in a molding system and their small size, the cleaning processtakes time, and adversely affects the productivity of the moldingsystem.

Another problem with the air vents 34 is the excess molding compoundwhich forms in the air vents 34. This excess molding compound issometimes referred to as mold “flash”. The flash fills the air vents 34causing blockage and defective packages 14. In addition, small pieces offlash can break loose from the air vents and stick to the leadframe 10.The pieces of flash can cause shorting in the completed packages 14, andcan also accumulate on various process equipment, such as conveyortracks, causing additional problems. Often times the flash pieces arecharged such that they are attracted to metal surfaces.

The present invention is directed to a system and to a method formolding semiconductor components in which additional runners areemployed to channel the molding compound through corners of the moldcavities that must normally be vented. This eliminates a large number ofair vents, and alleviates the cleaning and flash accumulation problemsassociated with the air vents.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved system forfabricating semiconductor components, an improved method for fabricatingsemiconductor components, and improved semiconductor componentsfabricated using the system and the method are provided.

In an illustrative embodiment, the system and the method are used tofabricate plastic semiconductor packages on a metal leadframe. Theleadframe is configured to support semiconductor dice in pairs twoabreast for molding. In addition, the leadframe includes leadfingerswire bonded to the dice, and configured to form the internal andexternal leads for the packages.

The system includes an upper mold cavity plate having a plurality ofupper mold cavities, and a lower mold cavity plate having a plurality oflower mold cavities. The upper mold cavity and the lower mold cavity areconfigured to engage opposing surfaces of the leadframe, and to mold theplastic packages onto the leadframe. In addition, each mold cavity plateincludes corner runners configured to channel molding compound throughthe corners of the mold cavities, and into dummy cavities on opposingsurfaces of the leadframe. The flow of molding compound through thecorners prevents trapped air from accumulating in the corners. Eachdummy cavity is in flow communication with a single air vent, and anytrapped air in the molding compound is channeled through the dummy moldcavities and into the air vents. The runners eliminate the corner airvents of the prior art molding system such that there are fewer airvents to clean and less flash particles are produced.

The method includes the step of providing the upper mold cavity and thelower mold cavity with the mold cavities, the runners, the dummycavities and the air vents. The method also includes the steps ofinjecting the molding compound into the mold cavities, and directing themolding compound proximate to the corners of the mold cavities using therunners. In addition, the method includes the step of directing trappedair through the runners into the dummy mold cavities, and then out theair vents.

Each semiconductor package includes a semiconductor die, and upper andlower body segments encapsulating the die and a portion of theleadframe. Prior to singulation of the packages, the leadframe includesupper dummy segments and lower dummy segments on upper and lowersurfaces thereof proximate to an edge of the leadframe. The leadframealso includes a connecting dummy segment on the lower surface thereofbetween adjacent pairs of packages. In addition, the leadframe includessecond dummy segments on the lower surface thereof connected to thelower dummy segments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view illustrating a prior artmethod for molding a semiconductor package using multiple vents locatedproximate to the corners of the package;

FIGS. 2A–2D are schematic cross sectional views illustrating a systemconstructed in accordance with the invention, and steps in a method forfabricating semiconductor packages in accordance with the invention;

FIG. 3A is a bottom view of an upper mold cavity plate of the systemtaken along line 3A—3A of FIG. 2A;

FIG. 3B is a side elevation view of the upper mold cavity plate;

FIG. 3C is an enlarged view of a portion of the upper mold cavity platetaken along dotted segment 3C of FIG. 3A illustrating upper moldcavities on the upper mold cavity plate;

FIG. 3D is a side elevation view of the upper mold cavities;

FIG. 3E is an enlarged view of a portion of the upper mold cavity platetaken along dotted segment 3E of FIG. 3A illustrating a dummy moldcavity on the upper mold cavity plate;

FIG. 3F is a side elevation view of the dummy mold cavity;

FIG. 3G is an end view of the dummy mold cavity;

FIG. 4A is a plan view of a lower mold cavity plate of the system takenalong line 4A—4A of FIG. 2A;

FIG. 4B is a side elevation view of the lower mold cavity plate;

FIG. 4C is an enlarged view of a portion of the lower mold cavity platetaken along dotted segment 4C of FIG. 4A illustrating lower moldcavities on the lower mold cavity plate;

FIG. 4D is a side elevation view of a lower mold cavity;

FIG. 4E is an enlarged view of a portion of the lower mold cavity platetaken along dotted segment 4E of FIG. 4C illustrating a connecting dummycavity on the lower mold cavity plate;

FIG. 4F is a side elevation view of the connecting dummy cavity;

FIG. 4G is an end elevation view of the connecting dummy cavity;

FIG. 4H is an enlarged view of a portion of the lower mold cavity platetaken along dotted segment 4H of FIG. 4C illustrating a dummy moldcavity on the lower mold cavity plate;

FIG. 4I is an end elevation view of the dummy mold cavity;

FIG. 4J is a side elevation view of the dummy mold cavity;

FIG. 5 is an enlarged plan view taken along line 5—5 of FIG. 2Billustrating a leadframe configured for constructing packages inaccordance with the invention;

FIG. 6 is a cross sectional view taken along section line 6—6 of FIG. 2Cillustrating a flow of a molding compound on an upper surface of theleadframe during a molding step;

FIG. 7A is a plan view taken along line 7A—7A of FIG. 2D illustratingsemiconductor packages on the leadframe constructed using the system andmethod of the invention; and

FIG. 7B is a side elevation view of the semiconductor packages on theleadframe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 2A–2D, a system 40 for fabricating semiconductorcomponents, and steps in a method for fabricating the semiconductorcomponents using the system 40 are illustrated. In the illustrativeembodiment, the components comprise semiconductor packages 52 (FIG. 2D)having a TSOP (thin small outline package) configuration. However, it isto be understood that the system 40, and the method, can be used tofabricate other types of semiconductor components, such as chip scalepackages, BGA devices, multi chip modules and other types of plasticpackages (e.g., DIPs, SIPs etc.).

Referring to FIG. 2A, the system 40 includes a transfer moldingapparatus 58. One suitable transfer molding apparatus 58 is manufacturedby ASAHI Engineering Company of Japan and is designated a “COSMO” model.

The system 40 also includes an upper mold cavity plate 42U, and a lowermold cavity plate 42L. The upper mold cavity plate 42U and the lowermold cavity plate 42L are movable by the transfer molding apparatus 58between an open position (FIG. 2A), and a closed position (FIG. 2C).However, as is apparent the “upper” and “lower” terminology is forillustrative purposes, and would change according to the orientation ofthe system 40. Accordingly, the claims to follow refer generically to “afirst mold cavity plate” (i.e., upper mold cavity plate 42U) and to “asecond mold cavity plate” (i.e., lower mold cavity plate 42L).

Referring to FIG. 2B, for performing a molding step of the method, aleadframe 46 is placed between the upper mold cavity plate 42U and thelower mold cavity plate 42L. The transfer molding apparatus 58 caninclude suitable mechanisms (not shown) for placing and aligning theleadframe 46 between the mold cavity plates 42U, 42L. However, prior tothe molding step, a plurality of semiconductor dice 56 (FIG. 5) areattached to the leadframe 46. The leadframe 46 includes an upper surface47U on which the dice are mounted, and a lower surface 47L. In addition,as shown in FIG. 5, the leadframe 46 includes a plurality of leadfingers 60, and the dice 56 are wire bonded to the lead fingers 60. Theleadframe 46 can also include a plurality of mounting paddles (notshown) for supporting the dice 56.

As shown in FIG. 5, the lead fingers 60 are initially connected by a busbar 62, but following a trim and form step, will become the externalleads for the semiconductor packages 52. As also shown in FIG. 5, theleadframe 46 includes handling openings 68A, 68B, 68C, and thermalexpansion slots 66 that function substantially as previously described.In addition, the leadframe 46 includes mold inlet openings 64,connecting segment openings 70, and dummy segment openings 72 configuredto facilitate the flow of the molding compound 50 and the formation ofthe molded features on the leadframe 46.

Referring to FIG. 2C, during the molding step, the upper mold cavityplate 42U and the lower mold cavity plate 42L are clamped by thetransfer molding apparatus 58 to the upper surface 47U and the lowersurface 47L of the leadframe 46. As also shown in FIG. 2C, the system 40includes a molding compound source 48 configured to inject a moldingcompound 50 (FIG. 6) under pressure between the upper mold cavity plate42U and the lower mold cavity plate 42L. The flow of the moldingcompound 50 (FIG. 6) during the molding step will be more fullyexplained as the description proceeds. Also during the molding step, airis vented from the upper mold cavity plate 42U and the lower mold cavityplate 42L through upper air vents 84U, and lower air vents 84L asindicated by air flow arrow 54. Although there are a plurality of airvents 84U, 84L, a single upper air vent 84U and a single lower air vent84L is associated with each pair of packages 52 on the leadframe 46.

Referring to FIG. 2D, following the molding step the leadframe 46includes a plurality of semiconductor packages 52. The leadframe 46 withthe semiconductor packages 52 thereon is also shown in FIGS. 7A and 7B.Each semiconductor package 52 includes an upper body segment 74 and alower body segment 76, having matching thicknesses and peripheraloutlines. However, it is to be understood that the invention can also bepracticed to form a molded body segment on only one side of asemiconductor component, or to form a component having asymmetricalmolded body segments.

As also shown in FIG. 2D, the leadframe 46 includes upper dummy segments80 and lower dummy segments 82 located proximate to a right lateral edge98 of the leadframe 46. In addition, the leadframe 46 includesconnecting dummy segments 78 located between adjacent semiconductorpackages 52. The structure and function of the dummy segments 78, 80, 82will be more fully explained as the description proceeds.

Referring to FIGS. 3A–3D, the upper mold cavity plate 42U isillustrated. The upper mold cavity plate 42U is preferably machined outof a single block of a metal, such as stainless steel. As shown in FIG.3A, the upper mold cavity plate 42U has a generally rectangularperipheral shape which corresponds to, but is slightly larger than therectangular peripheral shape of the leadframe 46.

As also shown in FIG. 3A, the upper mold cavity plate 42U includes aplurality of upper mold cavities 86U, which are arranged in pairscorresponding to the locations of the semiconductor dice 56 (FIG. 5) onthe leadframe 46. The upper mold cavities 86U are configured to mold theupper body segments 74 (FIG. 2D) of the packages 52 (FIG. 2D). The uppermold cavity plate 42U also includes upper dummy mold cavities 102Uconfigured to mold the upper dummy segments 80 (FIG. 2D) on theleadframe 46.

As shown in FIG. 3B, the upper mold cavity plate 42U also includeshandling recesses 88U on opposing sides thereof. In addition the uppermold cavity plate 42U includes stepped surfaces 90U on opposing endsthereof.

As shown in FIG. 3C, the upper mold cavity plate 42U also includesopenings 92U in the upper mold cavities 86U configured to receiveknockout pins for pushing the semiconductor packages 52 (FIG. 2D) out ofthe upper mold cavities 86U. In addition, the upper mold cavity plate42U includes through holed openings 94U configured to for use withassociated ejector pins for ejecting the leadframe 46.

As also shown in FIG. 3C, the upper mold cavity plate 42U includes inletrunners 96U configured to receive the molding compound 50 (FIG. 6) fromthe molding compound source 48 (FIG. 2C), and to direct the moldingcompound 50 into the upper mold cavities 86U. In addition, the uppermold cavity plate 42U includes connecting runners 100U configured todirect the molding compound 50 between adjacent pairs of upper moldcavities 86U. Further, the upper mold cavity plate 42U includes cornerrunners 106U configured to direct the molding compound 50 into thecorners 108U of the upper mold cavities 86U. As will be furtherexplained, the corner runners 106U prevent air from being trapped in thecorners 108U of the upper mold cavities 86U, and allow the air vents 34(FIG. 1) of the prior art system to be eliminated. In addition, thecorner runners 106 improve the construction of the packages 52 becausethe corners thereof do not include trapped air.

As shown in FIG. 3C, the upper mold cavity plate 42U also includes dummyrunners 110U configured to direct the molding compound 50 from the uppermold cavities 86U into the dummy cavities 102U. In addition, the uppermold cavity plate 42U includes the upper air vents 84U configured tovent air from the dummy mold cavities 102U to atmosphere. Each pair ofupper mold cavities 86U has a single upper air vent 84U associatedtherewith. However, all of the air vents 84U are in flow communicationand vent to atmosphere.

During the molding step, the inlet runners 96U, the corner runners 106U,the connecting runners 100U, and the dummy runners 110U, in combinationwith the upper surface 47U (FIG. 2B) of the leadframe 46, form closedconduits for channeling the flow of the molding compound 50 over theupper surface 47U of the leadframe 46.

Still referring to FIG. 3C, the upper mold cavities 86U includeperipheral lips 104U which are also known as “clamping surfaces” whichare configured to engage the upper surface 47U of the lead frame 46. Theperipheral lips 104L are the highest surfaces on the upper mold cavityplate 42U and sealingly engage the upper surface 47U of the lead frame46 for forming the upper body segments 74 of the packages 52. Inaddition, the peripheral lips 104U space the runners 96U, 106U, 100U,110U from the upper surface 47U of the leadframe 46 such that themolding compound 50 can flow between the runners 96U, 106U, 100U, 110Uand the upper surface 47U of the leadframe 46.

One method for fabricating the peripheral lips 104L is to EDM (electricdischarge machine) the cross hatched area 112U which surrounds theperipheral lips 104L to a selected depth. By way of example, this crosshatched area 112U can be EDMed to a depth measured from the surfaces ofthe peripheral lips 104L of about 1.01 to 1.78 mm. Similarly, the inletrunners 96U, the corner runners 106U, the connecting runners 100U, thedummy runners 110U and the air vents 84U can be EDMed to selected depthswith respect to the surfaces of the peripheral lips 104L. By way ofexample, the depth of the inlet runners 96U, the connecting runners 100Uand the dummy runners 110U can be about 0.005–0.008 mm. The depth of thecorner runners 106U and the air vents 84U can be about 0.025 mm. In FIG.3C, areas that have the same depth are cross hatched with the samesection lines.

FIG. 3D illustrates the depth of the upper mold cavities 86U which isabout 10 times greater than the depths of the runners 96U, 106U, 100U,110U listed above. Accordingly, for simplicity FIG. 3D does notillustrate the depth of the runners 96U, 106U, 100U, 110U or the heightof the peripheral lips 104U relative to the runners. By way of example,the upper mold cavities 86U can be EDMed to a depth of about 0.445 mm.In addition, the upper mold cavities 86U can have a length of about18.40 mm and a width of about 14.000 mm. The inlet runners 96U can havea width of about 5.00 mm. The corner runners 106U can have a length ofabout 4.00 mm, and a width of about 0.8 mm. The peripheral lips 104U canhave a width of about 0.8 mm.

Referring to FIGS. 3E–3G, a dummy mold cavity 102U and associated airvent 84U are illustrated. The dummy mold cavities 102U can have a depthof about 0.445 mm, a length of about 7.20 mm and a width of about 1.30mm. However, as is apparent, all of the dimensions given above aremerely exemplary, and can be adjusted as required by the skilledartisan.

Referring to FIGS. 4A–4I, the lower mold cavity plate 42L is shown. Thelower mold cavity plate 42L is constructed substantially in a mirrorimage of the upper mold cavity plate 42U. In addition, the lower moldcavity plate 42L has the same size and shape as the upper mold cavityplate 42U includes the same stepped surfaces 90L as opposing ends. Inaddition, the lower mold cavity plate 42L includes lower mold cavities86L having peripheral lips 104L (FIG. 4C) configured to sealingly engagethe lower surface 47L of the leadframe 46. The lower mold cavities 86Land the upper mold cavities 86U form enclosed spaces which substantiallydetermine the size and shape of the semiconductor packages 52 (FIG. 2D).The peripheral lips 104U of the lower mold cavities 86L are defined byEDMed surface 112L. The lower mold cavity plate 42L also includesopenings 92L for knock out pins.

The lower mold cavity plate 42L also includes inlet runners 96L, cornerrunners 106L, connecting runners 106L, dummy runners 110L, dummy moldcavities 102L and air vents 84L. These elements are constructedsubstantially as mirror images of the equivalent elements contained onthe upper mold cavity plate 42U. However, there are some differencesbetween these elements. Specifically, as shown in FIG. 4C, the inletrunners 96L include faceted surfaces.

In addition, as shown in FIGS. 4E–4G, the connecting runners 100Linclude a connecting dummy cavity 114L, configured to form theconnecting dummy segment 78 (FIG. 2D) between the packages 52. As shownin FIG. 4E, the connecting dummy cavity 114L is generally circular inshape with faceted surrounding surfaces. Further, as shown in FIGS.4H–4I, the dummy runners 110L include a second dummy cavity 116Lconfigured to form a second lower dummy segment 118 (FIG. 2D) on theleadframe 46. As shown in FIG. 4H, the second dummy cavity 116L isgenerally circular in shape with faceted surrounding surfaces.

Referring to FIG. 6, the flow of the molding compound 50 over the uppersurface 47U of the leadframe 46 during the molding step is illustrated.As indicated by flow arrows 120, the molding compound 50 enters theinlet runners 96U and is directed into the upper mold cavities 86U (FIG.3C). In general, the flow of the molding compound 50 is from left toright in FIG. 6, from the left lateral edge 99 of the leadframe 46towards the right lateral edge 98 of the leadframe 46. However, as isapparent the “right” and “left” terminology is for illustrativepurposes, and would change according to the orientation of the leadframe46. Accordingly the claims to follow refer generically to a “first edge”(i.e., left lateral edge 99) and to a “second edge” (i.e., right lateraledge 98).

The corner runners 106U also direct the molding compound 50 proximate tothe corners 108U (FIG. 3C) of the upper mold cavities 86U such that thecorners 124 of the packages 52 do not include voids and trapped air 120.Each corner 124 includes orthogonal surfaces such that the cornerrunners 106U direct the flow of the molding compound 50 through thecorner 124 in a direction generally perpendicular to one corner surfaceand generally parallel to the other corner surface. With the cornerrunners 106U directing the flow of the molding compound through thecorners 124, there is no need to vent the corners 108U (FIG. 3C) of theupper mold cavities 86U.

In the illustrative embodiment the corner runners 106 are configured toinitially direct the molding compound 50 along outside edges of theupper mold cavities 86U on the left lateral edge 99 of the leadframe 46in a flow direction generally perpendicular to the flow of the moldingcompound through the inlet runners 96U. In addition, the corner runners106U are configured to turn the flow direction of the molding compoundapproximately 90° such that the molding compound 50 enters the corners108U of the upper mold cavities 86U on the left lateral edge 99 of theleadframe 46 in a flow direction that is generally parallel to the flowdirection through the inlet runners 96U.

The molding compound 50 is also directed through the connecting runners100U into the adjacent mold cavities 86U. The flow direction through theconnecting runners 100U is generally parallel to the flow directionthrough the inlet runners 96U. The corner runners 106U are configured toturn the molding compound 50 exiting the upper mold cavities 86U on theleft lateral edge 99 of the leadframe 46 approximately 90° and towardsthe connecting runners 100U, then 180° and away from the connectingrunners 100U.

The molding compound 50 is also directed through the dummy runners 110Uand into the dummy mold cavity 102U. Any trapped air 122 is alsodirected into the dummy mold cavity 102U and is vented through the airvent 84U to atmosphere. The corner runners 106U are configured to turnthe molding compound 50 exiting the upper mold cavities 86U on the rightlateral edge 99 of the leadframe 46 approximately 90° , and to directthe molding compound towards the dummy runners 110U. The corner runners106U then turn the flow of the molding compound approximately 90° in adirection generally parallel to the flow direction through the dummyrunners 110U and the dummy mold cavities 102U.

The flow of the molding compound over the lower surface 47L (FIG. 2C) ofthe leadframe 46 is substantially the same as described above, exceptthe connecting dummy segment 78 (FIG. 2C) and the second lower dummysegment 118 (FIG. 2C) are also formed and function as package to packagerunners.

Thus the invention provides a system and a method for fabricatingsemiconductor components, and improved semiconductor componentsfabricated using the system and the method. While the invention has beendescribed with reference to certain preferred embodiments, as will beapparent to those skilled in the art, certain changes and modificationscan be made without departing from the scope of the invention as definedby the following claims.

1. A method for fabricating semiconductor components on a substratecomprising: providing a plate comprising at least one cavity configuredto receive a molding compound and to mold a body segment of a componenton the substrate, the cavity having at least one corner; providing atleast one corner runner on the plate configured to direct the moldingcompound through the corner; providing at least one dummy cavity on theplate in flow communication with the cavity and the corner runner;providing a vent on the plate in flow communication with the dummycavity; injecting the molding compound into the cavity and the dummycavity; and venting the air through the vent during the injecting step.2. A method for fabricating semiconductor components on a substratecomprising: providing a plate comprising a plurality of cavitiesconfigured to receive a molding compound and to mold body segments ofthe components on a surface of the substrate, the cavities having aplurality of corners; providing a plurality of corner runners on theplate configured to direct the molding compound through the corners andto prevent air from accumulating in the corners; providing a vent on theplate in flow communication with the cavities and the corner runners;providing a dummy cavity on the plate in flow communication with thecorner runners and the vent; injecting the molding compound into thecavities and molding the body segments on the surface; collecting theair in the dummy cavity; and venting the air through the vent.
 3. Amethod for fabricating semiconductor components on a substratecomprising: providing a plate comprising a plurality of cavitiesconfigured to receive a molding compound and to mold body segments ofthe components on a surface of the substrate, the cavities having aplurality of corners having orthogonal surfaces; providing a pluralityof corner runners on the plate configured to direct the molding compoundgenerally parallel to and generally perpendicular to the orthogonalsurfaces to prevent air from accumulating in the corners; providing avent on the plate in flow communication with the cavities and the cornerrunners; injecting the molding compound into the cavities and moldingthe body segments on the surface; and venting the air through the ventduring the injecting step.
 4. The method of claim 3 wherein thesubstrate comprises a leadframe and the components comprisesemiconductor packages.
 5. A method for fabricating a semiconductorcomponent on a substrate comprising: providing a plate comprising acavity configured to receive a molding compound and to mold a bodysegment of the component on the substrate, the cavity having a corner;providing a first runner on the plate configured to direct the moldingcompound through the corner and to prevent trapped air in the moldingcompound from accumulating in the corner; providing a second runner onthe plate in flow communication with the first runner, the first runnerand the second runner configured to change a flow direction of themolding compound; providing an air vent on the plate in flowcommunication with the second runner; and molding the body segment tothe substrate using the cavity with the first runner directing themolding compound through the corner and the second runner directing thetrapped air to the air vent.
 6. A method for fabricating a semiconductorcomponent on a substrate comprising: providing a plate comprising acavity configured to receive a molding compound and to mold a bodysegment of the component on the substrate, the cavity having a corner;providing a dummy cavity on the plate in flow communication with thecavity and the air vent configured to mold a dummy segment on thesubstrate; providing a runner on the plate configured to direct themolding compound through the corner and to prevent trapped air in themolding compound from accumulating in the corner; providing an air venton the plate in flow communication with the runner; molding the bodysegment to the substrate using the cavity with the runner directing themolding compound through the corner and the trapped air to the air ventand with the air vent venting the trapped air; and molding the dummysegment during the molding step.
 7. The method of claim 6 furthercomprising providing a second cavity on the plate in flow communicationwith the air vent, the cavity and a second runner configured to directthe molding compound through a second corner of the second cavity, thenmolding a second body segment for a second component on the substrateusing the second cavity and the second runner.
 8. The method of claim 6wherein the substrate comprises a leadframe and the component comprisesa semiconductor package.
 9. A method for fabricating a semiconductorcomponent on a substrate comprising: providing a plate comprising acavity configured to mold a body segment for the component on a surfaceof the substrate and having a corner; providing an inlet runner on theplate configured to direct a molding compound into the cavity; providinga corner runner on the plate configured to direct the molding compoundthrough the corner and to prevent trapped air in the molding compoundfrom accumulating in the corner; providing a dummy cavity on the plateconfigured to mold a dummy segment on the substrate; providing an airvent on the substrate in flow communication with the dummy cavity; andmolding the body segment and the dummy segment on the substrate usingthe cavity with the corner runner directing the trapped air into thedummy cavity and the air vent venting the trapped air.
 10. The method ofclaim 9 wherein the substrate comprises a leadframe and the componentcomprises a semiconductor package.
 11. The method of claim 9 furthercomprising providing a pair of mold cavities on the plate configured tomold body segments on the substrate for a pair of components, providinga second corner runner configured to direct the molding compound througha second corner of the second cavity, providing a connecting runnerconfigured to direct the molding compound between the pair of moldcavities, then molding the body segments while directing the moldingcompound through the second corner into the dummy cavity and venting thetrapped air through the air vent.
 12. The method of claim 9 wherein thecorner includes orthogonal surfaces and the corner runner is configuredto direction the molding compound generally parallel to one surface andgenerally perpendicular to another surface.
 13. The method of claim 9wherein the component comprises a semiconductor package comprising a dieand the body segment encapsulates the die.
 14. The method of claim 9further comprising providing a second plate substantially identical tothe plate configured to mold an opposing body segment for the componenton an opposing surface of the substrate then molding the opposing bodysegment during the molding step.
 15. The method of claim 9 furthercomprising providing a plurality of cavities on the plate configured tomold a plurality of body segments for a plurality of components on thesubstrate, the cavities having a plurality of corners and a plurality ofcorner runners configured to direct the molding compound through thecorners then molding the body segments during the molding step.
 16. Themethod of claim 9 wherein the plate is mounted to a transfer moldingapparatus and the molding step is performed using the transfer moldingapparatus.
 17. A method for fabricating semiconductor componentscomprising: providing a substrate; providing a first plate comprising aplurality of first mold cavities configured to mold first body segmentsfor the components on the substrate; providing a first runner on thefirst plate configured to direct a molding compound into the firstcavities; providing a plurality of first corner runners on the firstplate configured to direct the molding compound through first corners inthe first cavities and to prevent air in the molding compound fromaccumulating in the first corners; providing a vent on the first platein flow communication with the first runner and the first cornerrunners; and molding the first body segments to the substrate using thefirst cavities with the first runner and the first corner runnersdirecting the molding compound through the first cavities, and with theair venting through the air vent.
 18. The method of claim 17 furthercomprising: providing a second plate comprising a plurality of secondmold cavities configured to mold second body segments for the componentson the substrate; providing a second runner on the second plateconfigured to direct the molding compound into the second cavities;providing a plurality of second corner runners on the second plateconfigured to direct the molding compound through second corners in thesecond cavities and to prevent the air in the molding compound fromaccumulating in the second corners; providing a second vent on thesecond plate in flow communication with the second runner and the secondcorner runners; and molding the second body segments to the substrateusing the second cavities with the second runner and the second cornerrunners directing the molding compound through the second cavities, andwith the air venting through the air vent.
 19. The method of claim 18further comprising providing the substrate with a plurality of openingsconfigured to direct the molding compound on opposing sides of thesubstrate.
 20. The method of claim 18 wherein the substrate comprises aleadframe and the components comprise semiconductor packages.